This invention relates, in general, to semiconductor devices, and more particularly, to a non-silicon and silicon bonded structure and method of manufacture.
It may be desirable to bond a non-silicon substrate to a silicon substrate. Although silicon-to-silicon wafer bonding is well known, the bonding of a silicon substrate to a non-silicon substrate is not as straightforward.
The bonding of a non-silicon substrate, such as gallium arsenide, to a bare silicon substrate or a silicon substrate having a silicon dioxide layer formed thereon has been accomplished. Bonding is accomplished by bringing the substrates together and annealing. The thermal expansion coefficient of gallium arsenide is much larger than that of silicon or silicon dioxide, so that the gallium arsenide expands more during high temperature processing. When the bonded structure is cooled to room temperature, defects are created at the interface between the gallium arsenide substrate and the silicon substrate (or the silicon dioxide layer, if present) due to the stress created by the difference in thermal expansion coefficients of the silicon substrate or the silicon layer and the gallium arsenide substrate. The presence of silicon dioxide between the silicon substrate and the non-silicon substrate may help to reduce some of the stress because it is amorphous. However, it would be desirable to further reduce the stress to further lower the presence of defects.
A way to relieve the stress in a bonded non-silicon and silicon structure has been accomplished by cutting or etching the non-silicon substrate into small pieces after bonding. This, however, is an unduly complicated process. The stress, and thus the number of defects formed, may be lowered by lowering the temperature at which the anneal is done during bonding. However, it may be desirable to use a high temperature anneal to increase the bonding strength between the non-silicon substrate and the silicon substrate or the silicon dioxide. Furthermore, it is necessary to use high temperature processing to form semiconductor devices in the non-silicon substrate after bonding, thus high temperature processing can not be avoided.
By now it should be appreciated that it would be advantageous to provide an improved method of bonding a non-silicon substrate to a silicon substrate and reduce the number of defects formed during high temperature processing.
Accordingly, it is an object of the present invention to provide a stress-free non-silicon and silicon bonded structure and method of manufacture.
Another object of the present invention is to provide an improved method of bonding a non-silicon substrate to a silicon substrate.
A further object of the present invention is to provide an improved non-silicon and silicon bonded structure which can be subjected to high temperature processing without creating defects.
An additional object of the present invention is to provide an improved non-silicon and silicon or quartz bonded structure wherein the silicon or quartz provides an ideal supporting material for the non-silicon substrate.
Yet another object of the present invention is to provide a non-silicon and silicon bonded structure having a stress-relief layer between them.